摘要：
For understanding the adaptability and countermeasures of Davidia involucrata var.vilmoriniana (Dode) Wange seedlings to drought stress, the effects of drought stress on the related substances of antioxidant enzymes in its seedlings were studied.Drought stress treatment were made for 3-year-old Davidia involucrata var.vilmoriniana (Dode) Wange seedlings with different concentration of control group, and 5％, 10％, 15％ and 20％ PEG-6000 gradients, and a comparative study was conducted after extraction of CAT, CAT and MDA from its leaves.The results showed that: (1) With the severity of drought stress and the prolongation of stress time, RWC decreased rapidly, the enzyme activity of SOD, POD and CAT increased at the beginning, and then descended, MDA contents decreased at the beginning and then increased; (2) There was no significance change on SOD, and SOD played a minimal role in the drought resistance mechanism.POD activity and CAT activity changed significantly, and they worked synergistically as scavenging free radicals under different stress; (3) POD activity was 409.14％ higher than CK under slight stress with 24 h, CAT activity was 191.49％ higher than CK under severe stress.Both POD and CAT decreased and close to CK under very severe st tress (20％PEG).This indicated that with the increase of drought stress, CAT played a major role in protecting membrane lipids, and their activities decreased under very severe stress; (4) The content of MD decreased at the beginning and then increased, which indicated that in the early stage of drought stress, the production of MDA was reduced under the synergistic action of protective enzymes.The accumulation of protective enzymes under very severe stress increased to 29.86％ of CK, which indicated that the activity of protective enzymes was significantly inhibited with the increase of drought stress.The study showed that Davidia involucrata var.vilmoriniana (Dode) Wange is sensitive to drought stress and water factor is the critical element for its growth.%通过研究干旱胁迫对光叶珙桐幼苗抗氧化酶系统相关物质的影响,以探究光叶珙桐幼苗对干旱胁迫的适应能力.设置对照组、5％、10％、15％、20％PEG-6000梯度浓度对3年生光叶珙桐幼苗进行干旱胁迫处理,提取叶片中RWC、SOD、POD和CAT和MDA进行比较研究.结果表明:(1)随着光叶珙桐幼苗遭受干旱胁迫程度加剧与胁迫时间的延长,叶片中RWC急剧减少,SOD、POD与CAT酶活均先上升后下降,MDA含量先下降后上升;(2)SOD变化不显著,在光叶珙桐抗旱机制中发挥的作用最小;而POD活性和CAT活性均变化明显,二者协同作用,在不同程度的胁迫下分别起到清除自由基的作用,以降低自由基对植株造成伤害;(3)POD活性在24h轻度胁迫处理下高出CK组409.14％,CAT在重度胁迫处理下高出CK组191.49％,二者在严重胁迫(20％PEG)处理下又降至接近CK组水平,说明POD在轻度胁迫时POD发挥其保护作用,随着干旱胁迫程度的加剧,CAT发挥着保护膜脂的主要作用,在严重胁迫下二者活性均降低;(4)MDA含量先下降后上升,说明在干旱胁迫初期,在保护酶协同作用下减少了MDA的生成,在严重胁迫处理时含量积累升高到CK组含量的29.86％,表明随胁迫程度的加剧保护酶活性受到明显抑制.光叶珙桐对干旱胁迫较为敏感,水因子成为光叶珙桐生长的主要限制条件.
